This invention relates to a contact assembly for a plug connector, in particular for a PCB plug connector.
A generic contact assembly is known from European Patent 0 422 785. Such assembly comprises a carrier body formed of a plastic material and a plurality of contacts which are accommodated in the carrier body and each have two plug-in portions and one transition portion located between the two plug-in portions. The transition portions are exposed at least in part. The contacts are embedded within the carrier body by injection-molding. In the interior of the carrier body a recess is provided, through which the transition portions of the contacts freely extend. By appropriately choosing the exposed length of the transition portions, an impedance matching is to be achieved.
In some applications it may be desirable to mount a plug connector, equipped with the above-mentioned contact assemblies, on a printed circuit board by means of a reflow soldering method. In this method, a solder is applied onto the printed circuit board. Subsequently, the printed circuit board equipped with the plug connector is heated in an oven, so that the solder melts and the plug-in portions, which constitute contact pins and are plugged into the printed circuit board, are soldered to the printed circuit board.
In this method it is problematic that all contact pins must be heated as uniformly as possible, in order to obtain a consistently high quality of the soldered connection in all contact pins. It was found out that in the known contact assemblies a consistently good heating of the contacts is not ensured.
It is the object of the invention to improve a contact assembly as mentioned above such that a rather uniform and quick heating of all contacts is ensured.
This is achieved in a contact assembly comprising a carrier body formed of a plastic material and a plurality of contacts which are accommodated in the carrier body and each have two plug-in portions and one transition portion located between the two plug-in portions. The transition portions are exposed at least in part and the carrier body is provided with thermally conductive webs which are located between the transition portions and adjoin the latter. The invention is based on the finding that the air between the transition portions, which is present in prior art contact assemblies, acts as insulator and prevents a uniform heating of the contact pins. The thermally conductive webs primarily serve to uniformly distribute the heat between the various contacts. Since via their transition portion the longer contacts of a contact assembly basically absorb more heat than the shorter contacts, there is obtained a temperature gradient between the contacts. This temperature gradient is leveled out by the thermally conductive webs. In addition, the thermally conductive webs offer a large heat-exchanging surface for the warm air in the oven, which heat-exchanging surface approximately is as large as the exposed surface of the transition portions. This provides for a faster heating of the contacts, which provides for short process times. A positive side effect of the thermally conductive webs finally is the fact that they stabilize the carrier body. To provide for a free circulation of the air between the contact assemblies during reflow soldering, said carrier body is made as thin as possible, therefore, an additional stabilization is welcome.
The principle underlying the invention can be expressed in other words as follows: The carrier body of the contact assembly is made very thin, namely with a thickness which corresponds to the thickness of the transition portions of the contacts. The result is that the contacts are exposed on the outsides of the carrier body. The thickness of the carrier body is larger than the distance of adjacent contact columns. The result is that between the individual carrier bodies a comparatively large distance exists, so that the warm air in the oven can easily circulate between the carrier bodies.
In accordance with a preferred embodiment of the invention it is provided that on an outside of the carrier body the thermally conductive webs terminate flush with the transition portions. This allows an unhindered circulation of the heated air between adjacent contact assemblies.
In accordance with the preferred embodiment of the invention it is furthermore provided that on an outside of the carrier body the thermally conductive webs are connected with each other by at least one reinforcing web which extends transverse to the transition portions. The reinforcing web stabilizes the thermally conductive webs, so that the same cannot bulge or even buckle under an axial load acting on the contact assembly, as it may occur for instance when mounting the contact assemblies.
Preferably, it is provided that the carrier body has a reinforcing edge which is thicker than the thermally conductive webs, and that the carrier body has a holding web which is likewise thicker than the thermally conductive webs, the reinforcing edge being separated from the holding web by a circulation passage. Both the reinforcing edge and the holding web increase the mechanical strength of the carrier body, and they are exactly arranged in those regions in which forces acting on the plug-in portions of the contacts must be introduced into the carrier body. The circulation passage serves to specifically heat that contact which has the shortest transition portion and therefore always is the slowest to heat up, namely the contact at the transition between holding web and reinforcing edge.
In accordance with an alternative embodiment of the invention it may be provided that the contacts in the region of the exit from the carrier body are surrounded by injection-molding for about 270xc2x0. It was found out that to firmly anchor the contacts in the carrier body it is not necessary to completely embed the contact by injection-molding, thus, material can be saved.
Advantageous aspects of the invention can be taken from the sub-claims.